package cn.suchan.jianzhi.q50_array;

import java.util.ArrayList;

/**
 * 知识点：数组中重复的数字
 * 题目描述
 * 在一个长度为n的数组里的所有数字都在0到n-1的范围内。
 * 数组中某些数字是重复的，但不知道有几个数字是重复的。
 * 也不知道每个数字重复几次。请找出数组中任意一个重复的数字。
 * 例如，如果输入长度为7的数组{2,3,1,0,2,5,3}，那么对应的输出是第一个重复的数字2。
 *
 * @author suchan
 * @date 2019/06/09
 */
public class Solution {

    /**
     * 如果有重复的元素就返回true，否则返回false
     * 第一个出现的重复数字存放在duplication[0]中
     *
     * @param numbers     an array of integers
     * @param length      the length of array numbers
     * @param duplication (Output) the duplicated number in the array number,length of duplication array is 1,
     *                    so using duplication[0] = ? in implementation;
     *                    Here duplication like pointor in C/C++, duplication[0] equal *duplication in C/C++
     *                    这里要特别注意~返回任意重复的一个，赋值duplication[0]
     * @return true if the input is valid, and there are some duplications in the array number otherwise false
     */
    public boolean duplicate(int numbers[], int length, int[] duplication) {
        if (numbers == null || numbers.length <= 0) {
            length = 0;
            duplication[0] = -1;
            return false;
        }

        length = numbers.length;
        for (int i = 0; i < length - 1; i++) {
            if (numbers[i] > length - 1) {
                return false;
            }
            for (int j = i + 1; j < length; j++) {
                if (numbers[i] == numbers[j]) {
                    duplication[0] = numbers[i];
                    return true;
                }
            }
        }
        return false;
    }

    /**
     * 借助list
     *
     * @param numbers
     * @param length
     * @param duplication
     * @return
     */
    public boolean duplicate1(int numbers[], int length, int[] duplication) {
        if (numbers == null || numbers.length <= 0) {
            length = 0;
            duplication[0] = -1;
            return false;
        }

        length = numbers.length;
        ArrayList<Integer> list = new ArrayList();
        for (int i = 0; i < numbers.length; i++) {
            if (numbers[i] > length - 1) {
                return false;
            }
            if (!list.isEmpty() && list.contains(numbers[i])) {
                duplication[0] = numbers[i];
                return true;
            }
            list.add(numbers[i]);
        }
        return false;
    }

    public static void main(String[] args) {
        Solution solution = new Solution();
        int[] arr = {2, 1, 3, 1, 4};
        int len = 0;
        int[] duplication = new int[1];
        solution.duplicate1(arr, len, duplication);
        System.out.println(len + "  " + duplication[0]);
    }
}
